The team wanted to come up with a startup method that would deliver the benefits of a cold boot (a "fresh session" at startup, no power usage when off) while reducing the amount of time that it takes to load the operating system from disk to RAM.

To accomplish this, Microsoft has combined aspects of a traditional Windows shutdown with system hibernation, which saves the contents of your RAM to disk and then restores it to RAM at next boot. While a Windows shutdown currently closes all user programs (the "user session") and then all system services and processes (the "kernel session") completely before powering off, Windows 8 closes the user session and saves the rest of your RAM's content to disk. The kernel session can then be restored to RAM quickly at next boot - this is more speedy than traditional hibernation both because there's less data to restore to RAM from the disk (just the kernel session, as opposed to the kernel session and the user session), and because restoring hibernation files is a fully multithreaded process in Windows 8. If the feature works as well as it does in the Microsoft demo video, it is indeed quite impressive.

Microsoft notes that drivers are still initialized during this startup process, which means that driver and system updates should no longer require a "full" reboot of the system (something Microsoft has been promising since the Longhorn days). However, for those of you more comfortable with a traditional "full" shutdown, there are command line options to toggle the new feature on and off ("powercfg /hibernate off" which has the unfortunate side-effect of completely disabling hibernation), and also to initiate one-time full shutdowns ("shutdown /s /full").

According to Microsoft, these improvements should benefit users with SSDs and HDDs alike, and will be especially noticeable when paired with systems supporting UEFI, the BIOS replacement that is slowly being adopted by most major PC manufacturers and motherboard makers. For full details, as always, you can check out the very detailed post on the Building Windows 8 blog.

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52 Comments

Although I have heard people make comments about the amount of time it takes to start up a computer, I wouldn't go so far as to say that they are complaints. Also, those are generally situations where only near-instant-on would really make a difference. Unless they can drop boot times (including POST) to 5 seconds or less, the time and resources put into this new "feature" would be better spent elsewhere.

The reality is, even if the computer only takes 10 seconds to boot, I'm still going to turn it on and then find something else to do (get coffee, organize my desk, make a phone call). I'm not going to sit there watching the POST and Windows animations.Reply

For those of us wanting to keep their electricity bill down, faster boot times are a welcome site. It's not going to make or break my experience, but hey I just saved some time not waiting for my PC ... great!

I use my PC ~2-4 hours a day. Why in the world would I keep it running for 20+ hours eating up power?Reply

Fastest I've ever managed is 15 seconds from off to desktop using a Crucal M225 64Gb SSD within an Acer 1820ptz. 15 seconds. Obviously I'd turned off a load of services and disabled a few features but I didn't go so far as to vLite anything.

P.s. No matter how fast Windows 8 boots motherboard makers had better remove the 12 second plus or minus from their own initialization process!

I'd be happy with only 12s from power switch to OS boot loader. My i7-950 takes almost 30s to get to that point (I think it was a bit faster before I overclocked it by ~50%); from there it's about 15s from not only being logged in but having my apps starting up.Reply

That is impressive for a PC with a full size CPU, but not so much for a tablet. My iPad starts and powers off pretty much instantly. If they want Win8 on a tablet they might need to work on shorten that process a bit more.Reply